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Show 1881.] PROF. W. H. FLOWER ON THE ELEPHANT SEAL. 157 direct line of modification, only carrying it out to a more complete extent than have the ordinary Seals. As far as our imperfect knowledge of its osteology allows us to judge, in all points in the anatomy of the limbs in which the Pho-cidae differ from the land Carnivores, such as the general proportions of the bones, especially the shortness of the femur, the want of development of the calcaneal process, the articulation of the fifth metacarpal with the proximal row of carpal bones, the Elephant Seal presents the extreme of modification. The true Seals (Phocina?) have well developed claws on both the fore and hind feet; and the toes of the posterior limbs are subequal, the first and fifth being only slightly longer than the others ; and the interdigital menbrane does not extend beyond the toes. In the Elephant Seal the claws of the fore limb are reduced, and in the hind limb are absent or excessively rudimentary ; the first and fifth toes of this limb are greatly enlarged beyond the others, and the skin prolonged in lobes beyond the true end of the digit, producing a much greater modification of the whole foot from the terrestrial type, and causing a considerable superficial resemblance to the forked caudal appendage of a Cetacean or Fish. This character of the pedal extremity is possessed also by the Ste-norhynchince, which are in many respects intermediate between the Phocina? and the Cystophorince. Another and still more important character in the structure of the limbs, in which the Seals resemble the Cetacea and differ from all other known mammals, is most strongly marked in the Elephant Seals, as is well seen in the young skeleton mounted in the Museum of the College of Surgeons. It is that all the phalanges of both limbs (except the ungual phalanges) are ossified from three centres, an epiphysis being developed for each extremity, instead of a single epiphysis at the proximal extremity, as is the rule throughout the class. How far this occurs in other Pinnipeds is not certainly known. Stenorhynchus leptonyx, as shown in the not quite adult skeleton from New Zealand, presented to the Museum of the College of Surgeons by Mr. W . L. Crowther, F.R.C.S., resembles the Elephant Seal in this respect. Tn the true Seals of our hemisphere (Phocince), if it occurs, it is as a much less obvious and more transient condition, as I have not been able to detect the double epiphysis in any of the young skeletons in the Museum1. The modifications of the ossicula auditus have been already referred to as showing that the Elephant Seal presents an extreme form, though here also Stenorhynchus is its nearest congener. In the dentition also it has been shown that the characters by which Seals differ from other mammals are carried to their fullest extent in the Elephant Seal. The Leopard Seals {Stenorhynchus) may be regarded as showing the greatest perfection of the type, in the even row of exactly similar, finely developed, and sharply cusped, two-rooted molars; while in the Elephant Seal the same type has under-i In the pes of a young Phoca vitulina in the Oxford Museum there are traces of epiphyses on the distal as well as the proximal end of the metacarpal of the hallux. |